The invention concerns a metal material with a surface which is modified by bonding an aromatic group, optionally substituted by a functional group, on the surface. In one embodiment, an aromatic group is attached to the surface by electrochemical reduction of a diazonium salt containing the aromatic group. The metal material is brought into contact with a solution of the diazonium salt in a solvent and negatively polarized relative to an anode that is also in contact with the solution. A carbon-metal bond of the covalent type is formed.